The present invention pertains to a water trap for removing liquid water from the pressurized breathing circuit of a ventilator, respirator, anaesthesia unit, or similar device. In such devices, gas mixtures containing water vapor are delivered under pressure to a patient. Water vapor is added so that the inspired gases do not dry out the patient's lungs. Since the temperature of the air outside the gas line is lower than the temperature of the gas mixture inside, water vapor in the gas line partially condenses to form liquid water. Therefore, to prevent liquid water from entering the patient's lungs it is necessary to have some means for trapping, and permanently removing, the liquid water from the gas line.
Previous water traps, though useful, have been deficient in several important respects. Many water traps quickly fill up with water and then must be drained. Often the breathing circuit is interrupted while the trap is being emptied. Another problem with these prior traps is that valuable hospital staff time must be spent on monitoring and emptying the traps. Many small water traps require draining every hour, and clearly, the smaller the trap, the more frequently the trap must be drained. Small traps also pose the hazard that if the trap is disturbed, by patient movement or some other source, then water may be projected into the gas line and into the patient's lungs. Thus, with such prior art water traps it is advantageous to have the liquid water quickly and permanently removed from the trap so as to reduce the possibility of this occurrence.
If the trap is large, so as to reduce the frequency of monitoring and draining, then a substantial strain on the gas line results from the accumulated weight of the water. This weight restricts patient movement and may actually deform the gas line. Additionally, use of a large trap makes it necessary for the ventilator or other device to work harder, since a larger volume must be pressurized.
A further problem with previous traps relates to their configuration. The typical trap consists of a "T" in the gas line, with the water storage receptacle connected to the bottom portion. Such a configuration requires that the trap be oriented in a vertical or close to vertical position for proper functioning. If the trap is not so oriented, draining will be substantially impaired, and perhaps cease. This creates the hazard that upon any minor disturbance of the trap, from patient movement or any other source, water may be projected into the gas line and into the patient's lungs. Certainly, it would be a substantial contribution to have a trap which can continuously trap and drain liquid water, thereby permitting uninterrupted operation of the breathing circuit, and which can function in any orientation. As described below, the present invention possesses all of these advantages.
Those few water traps which do allow for continuous operation of the breathing circuit require a specific orientation for proper functioning. One such trap, as disclosed in U.S. Pat. No. 4,327,718, utilizes a membrane which is gas impervious and liquid pervious, with a receptacle for receiving the liquid water lying under the membrane. Such a configuration, though allowing for continuous draining and operation of the breathing circuit, necessitates that the trap be oriented in a vertical or close to vertical position for proper functioning.
Another trap, disclosed in U.S. Pat. No. 3,968,812, relies on a highly sensitive diaphragm Water accumulates on the diaphragm until the weight of the water causes the diaphragm to unseat, and the water then passes to a collecting bag. Clearly, in a crowded hospital room setting, where many large and cumbersome pieces of equipment may be present, the patient's safety is threatened if the water trap is not oriented properly by a hospital staff member, or, if once oriented properly, it then moves from its vertical orientation because of patient movement or some other disturbance. Additionally, hospital staff time is wasted rearranging equipment to provide for the necessary vertical orientation of the trap. Additionally, the diaphragm's proper functioning requires frequent checking and maintenance.